Laboratory evaluation of platelet dysfunction.

Platelet dysfunction, especially acquired forms, is a common cause of hemorrhage, especially when associated with trauma or surgery. Although the hereditary platelet function defects are generally rare, hereditary storage pool disease is common enough to be suspected in an individual, usually a child, with characteristic historical and clinical findings. The acquired platelet function defects, especially those resulting from drugs, are very common and should promptly be suspected in patients with easy and spontaneous bruising, mild-to-moderate mucosal membrane hemorrhage, or unexplained bleeding associated with trauma or surgery. The template bleeding time is generally useful as a screening test of platelet function, but a normal template bleeding time, in the face of a suggestive history, suggestive clinical findings, or in the patient frankly bleeding, is not reliable, and platelet aggregation or lumi-aggregation should be done in applicable clinical situations. Prolongation of the template bleeding time is an unreliable predictor of clinical bleeding propensity. The mainstay of therapy for all of these defects, if bleeding is important, is the liberal infusion of suitable numbers of platelet concentrates. The acquired platelet function defects should also be managed by attempts to treat or control the underlying disease, if possible, and offending drugs or potentially offending drugs should immediately be stopped.